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cambering iron idea for Tormek-style grinders

Hi all,

I got a wild hair to redo some of my bench planes with more consistent cambers. I have more than one of the smaller sizes and wanted one each to be different than dead-straight across. That's easy to do for a slight curve on the stones but either I don't have the patience or the technique for something more pronounced.

I have a Grizzly 10" wet grinder which is the poor-man's version of a Tormek that uses a horizontal bar to present the piece to the wheel. So ... I put a gentle curve on a piece of plywood with a plane and belt sander (maybe 1.5 mm), hogged a dado across it for a stop and glued in a scrap of ash about 3/4" square. I also put a strip of veneer down the center of the flat side of the ply to register the plane iron slot. Finally, I drilled a 3/8" hole in the center for a carriage bolt to hold the iron in place.

The jig is designed to rock slightly with the stop against the outside of the bar with the wheel spinning away from me. It's 3 1/2" wide to keep me from tipping it on edge and digging into a corner. I suppose it's possible to have different versions for different cambers but I did this more by feel. And it worked. I checked it against a square every so often and when it looked right, it was on to the stones. I did both a jack and my fore plane using the jig and am pleased with the results -- especially since it was free and only took 15 minutes to make.

Stewie; that camber is on the jig -- it's slightly convex on the bottom. It only took a minute to get a technique for rocking pressure on the side that was over the center of the stone as I slid it across the bar. The stock jig gives you a dead-flat edge. With this unit, I could add a very slight camber to maybe .75 mm if I kept going. Half a mm was plenty for the 2" jack. Plus, I have the bevel angle set so it is pretty consistent across the width. With the stone spinning away from me, it pulls the piece against the stop.

Eric; my jig for the water/diamond-stones is a big contraption that holds the blades firmly but rolls on a single wheel on the back end. It's easy enough to rock it side to side to polish up the work done by the Grizzly. I usually go to 1000 grit, 1500, 4000 and 8000. The latter two stones are a hair lower than the first two to increase the bevel. As well as it works for that, it was an eternity to get a consistent camber. It wants to make things straight. sh

PS: does anyone else feel slightly awkward using metric and stand measurements in the same paragraph? sh

Eric; if I'd needed it, this was the gizmo to use on the waterstones. By using a thick enough block, you could put a different radius on all four sides and turn it for better precision. I stole the idea from someone who had recessed bolts from the bottom going into a thin cap with T-nuts. That way, he could flip it upside down and put a back-bevel on the iron in a couple seconds. Since the bed for the wheel on my jig isn't the same height as the stones, it didn't enter into the design. sh

Patrick; I have something like that for rounding scrubbers and round bottom plane irons. This is a little different.

The bottom of the board that holds the iron is slightly rounded. The stop that holds against the back of the tool bar is straight but I suppose I could have put a small radius on that too. As I pass the iron back and forth on the wheel, I put pressure on either side so the convex bottom rocks on the straight tool bar. This approximates putting alternative side pressure on a water stone jig but it's a lot faster and yet still leaves a lot of control since you can control the pressure until you get exactly the shape you want.

Patrick; I have something like that for rounding scrubbers and round bottom plane irons. This is a little different.

The bottom of the board that holds the iron is slightly rounded. The stop that holds against the back of the tool bar is straight but I suppose I could have put a small radius on that too. As I pass the iron back and forth on the wheel, I put pressure on either side so the convex bottom rocks on the straight tool bar. This approximates putting alternative side pressure on a water stone jig but it's a lot faster and yet still leaves a lot of control since you can control the pressure until you get exactly the shape you want.

Yep, I understood what you'd done when I posted. That's why I noted that you "rounded it about the lengthwise axis" (where "lengthwise" is relative to the iron). That's definitely more work than just rounding off the leading edge about the iron's thickness axis as Derek did.

Note that when I say "rounded about an axis" I mean that that axis is the curve's center. In the case of your jig the center of the jig's curve (i.e. the center of the cylinder that would be formed if you extended that arc 360 deg) is parallel the lengthwise axis of the iron.

I understand the control argument, though I'm not completely sold on it. Definitely worth a try though. Thanks for posting!

The idea of making a slightly curved stop is intriguing. There's better science in getting this precise than I've spent. Putting a curve on the plywood amounted to ten seconds on the belt sander. Then I hogged a shallow dado on the radial saw until it fit a piece of scrap in the cutoff bin.

Using a highly curved stop like the scrub jig needs a little science of its own on one of these water wheel tool bars. You have to rotate the work so the radius on the jig needs to be less than what you want on the edge because the iron sticks out a couple inches. I reground a #5 sized Shelton iron for use as a scrubber with a 3" radius block and got a 5" radius edge. That turned out to work fine but it didn't occur to me before I did it. sh